More than 300 people were missing after a ferry sank off South Korea, the coastguard said on Wednesday, with a three-fold increase in the number of passengers unaccounted for put down to a miscalculation by officials.

The ferry was carrying 477 people, of whom 164 were confirmed rescued, coastguard officials said. Two people were confirmed dead after the ferry listed heavily onto its side and capsized in apparently calm conditions off South Korea's southwest coast.